1. Field of the Invention
The present invention relates to a method of forming a crystalline silicon film, and more particularly, it relates to a method of forming a crystalline silicon film which can provide its surface with a desired textured shape.
2. Description of the Background Art
In order to provide a surface of a silicon film with a textured shape, the generally employed methods involve roughening the surface by chemical or physical etching with an inert gas such as helium or argon, a fluorocarbon such as CF.sub.4, or a reactive gas such as gaseous hydrogen, or wet etching with KOH or nitric-hydrofluoric acid. In a textured surface obtained by such methods, however, intervals and heights of projecting portions are dispersed to result in a heterogeneously textured shape. In the aforementioned methods, further, the etchant is disadvantageously left on the etched textured surface.
A method of etching a (100) plane of a single-crystalline silicon film with a chemical agent such as sodium hydroxide or potassium hydroxide is known as a method of forming a relatively homogeneously textured surface (R. Hezel and L. Hu, Tech. Digest of the Int'l PVSEC-5 (1990), p. 701). According to this method, it is possible to obtain a relatively homogeneously textured shape as compared with a textured surface obtained by the aforementioned etching methods. However, this method is only applicable to a surface of a single-crystalline silicon film having a (100) plane. Further, it is impossible to form a desired textured shape since intervals and heights of projecting portions forming the textured shape depend on the lattice constant.